Apple Inc. has sent out invitations to a Sept. 10 event, where the world's largest technology company will unveil new models of the iPhone.

The event will be held at Apple's headquarters in Cupertino, Calif., at 10 a.m., the company said Tuesday in an emailed invitation designed with colorful bubbles. Apple will announce new iPhones at the event, a person familiar with the plans has said.

"This should brighten everyone's day," the company said in the invitation.

The iPhone, introduced in 2007, is Apple's top-selling product, accounting for half of revenue last year. As it faces increasing competition from rivals such as Samsung Electronics Co., the company is debuting an upgrade to the iPhone 5 as well as a less-expensive model, meant to help attract customers in developing regions.

Chief Executive Officer Tim Cook also will release an overhaul to Apple's iOS mobile operating system, which powers the company's iPhone, iPad and iPod Touch devices. Apple previewed the software's redesign in June, including changes to the e-mail, calendar and photo applications, as well as new fonts, icons and a brighter color scheme.

Underscoring the shifts in the technology industry since the first iPhone popularized touch-screen handheld computing, Finland's Nokia Oyj -- once the mobile-phone industry leader -- yesterday said it's selling its phone and services business to Microsoft Corp. after years of falling sales. Microsoft, the maker of Windows software for personal computers and mobile devices, also has struggled to gain a toehold in the phone business that's now dominated by Apple, Samsung and Google Inc.

Next week's event is Apple's first major product announcement since October 2012, when it released the iPad mini tablet. Later this year, the company is projected to introduce another update to its iPad line, giving it a fresh batch of products heading into the holiday shopping season.

The last time Apple hosted an event at its Cupertino base was in 2011, for the debut of the iPhone 4S, on the day before Apple co-founder Steve Jobs died.

Apple shares rose 0.3 percent to $488.58 at the close in New York. The stock has fallen 8.2 percent this year. The company, valued at about $444 billion, is the world's largest by market capitalization.